The invention relates generally to the use of large scale batteries in electrical vehicles and portable electronic devices. More specifically, the invention relates to a capacitor tub assembly used separately or in concert with conventional batteries, and a method for cooling the tub assembly
High end capacitors, such as ultra-capacitors, are high-energy, high-power density electrochemical devices that are easy to charge and discharge. They are basically capacitors that can store a lot more energy than standard electrolytic type capacitors. They store energy in a polarized liquid layer between an anode and cathode. As with conventional capacitors, the energy storage ability of an ultra-capacitor can be increased by increasing the surface area of the plates. Ultra-capacitors are commonly used as load leveling devices in electrical cars or vehicles, or portable electronics (such as portable computers). These new ultra-capacitors may be used alone or in concert with conventional batteries in order to extend the life of the conventional batteries by boosting the output of the batteries when power demand is at a peak.
One of the main advantages of an electric vehicle of any type is its capability to regenerate or recycle energy. Energy is generated in the electronic vehicle in order to brake the vehicle during sudden stops or de-acceleration. This energy may be recycled and used for re-acceleration of the vehicle, thus increasing the vehicle""s overall efficiency. The speed and efficiency with which the storage system is able to accept and return the energy flow is, clearly, the most important characteristic of the electronic vehicle""s performance. Due to acutely short deceleration response times, large amounts of energy are generated very quickly and only ultra-capacitors are capable of accepting and storing such a large scale inrush of energy in such a short cycle with minimum losses. Accordingly, ultra-capacitors could one day enable electronic vehicles to accelerate as quickly as conventional automobiles without sacrificing range, and even recharge during de-acceleration. Likewise, these ultra-capacitors could provide extra power for portable computers on initial power-up and during the operation of hard-drives, allowing manufacturers to use smaller batteries for the less demanding energy requirements of a computer.
However, when designing large arrays of high end capacitors, such as ultra-capacitors, for storing and providing large amounts of power, there are considerable design and safety requirements which must be considered, including equalization of power and voltage over all the capacitor cells, voltage and temperature considerations to ensure that the cells do not reach unsafe temperatures or pose dangerously high voltage threats to human personnel, discharge capability in the event of any errors or faults, and overall size and structure sufficient to house the capacitor cells while protecting the individual capacitor cells from operating environments and providing efficient usability and serviceability.
It therefore will be appreciated that there is a need for large arrays of capacitors for storing and providing large amounts of power within short cycle periods. These arrays must be properly designed to ensure that the capacitors evenly charge and discharge and do not reach high temperatures which could affect the operation of the capacitors. The present invention satisfies this need.
The present invention is directed toward a design for and method of fabricating an capacitor tub assembly which may be used alone or in concert with large scale batteries for powering electric vehicles and/or portable electronic devices. The capacitor tub assembly of the present invention preferably includes arrays of capacitor cells coupled in series and grouped into sub-packs. The capacitors within each sub-pack are electrically coupled via a unique printed circuit board (PCB) design, wherein individual PCBs cover the top and bottom ends of each sub-pack. Each sub-pack is further electrically coupled to at least two of the other adjacent sub-packs within the tub assembly, thereby ensuring that all the capacitor cells in the capacitor tub assembly are electrically coupled in series. The capacitor tub assembly is further comprised of voltage equalization circuitry which ensures even distribution of voltage and power over all of the individual capacitors within the tub assembly. The present invention further includes a cooling design and temperature electronics for monitoring the temperature and voltages of the individual capacitor cells within each sub-pack and cooling the individual capacitor cells (when necessary) from all four quarters. The capacitor tub assembly of the present invention further includes rapid discharge circuitry for discharging the capacitors to a safe voltage level in the event of a system fault or error in order to avoid danger to human personnel posed by the high voltages of these capacitors.
Finally, the present invention also includes a high voltage interlock (HVIL) switch. The HVIL switch is a two wire connection between high voltage components in the electric vehicle and the capacitor tub assembly. The HVIL switch operates as a safety switch between these high voltage components and the capacitor tub assembly. It prevents the components from being energized if any one of them is not properly installed within the vehicle and/or de-energizes the vehicle and discharges the capacitor assembly down to a safe voltage level if any of the components is compromised.